Copolymers of olefin such as ethylene and propylene which is a nonpolar monomer and a vinyl monomer containing polar group have been widely known. Specifically, ethylene-vinyl alcohol copolymers (EVOH) are random copolymer comprising ethylene and vinyl alcohol and synthesized by saponifying ethylene-vinyl acetate copolymers obtained by radical copolymerization of ethylene and vinyl acetate. EVOH is used in a wide range of fields for purposes such as food packages by taking advantage of its excellent gas barrier property.
The polymerization of monomers containing allyl group is more difficult compared to that of vinyl monomers, and the polymer of allyl group-containing monomers has been almost unheard. The main reason for this is that when allyl group-containing monomers are subjected to radical polymerization, the polymer propagation reaction proceeds very slowly due to the degradative chain transfer reaction to monomers and hence only oligomers having low degree of polymerization can be obtained (Chem. Rev. 58, 808 (1958)).
JP 2011-68881 A (International Publication No. WO 2011/025053; Patent Document 1) and J. Am. Chem. Soc., 133, 1232 (2011) (Non-patent Document 1) disclose coordination copolymerization of ethylene and polar group-containing allyl monomers using a catalyst of metal complex of group 10 elements in the periodic system, and polymers of polar group-containing allyl monomers are synthesized, which have not been obtained by a radical polymerization method. However, the weight average molecular weight (Mw) of the obtained polymer was about several thousands to several tens of thousands when calculated by employing polystyrene as an internal standard substance, and it has been difficult to obtain a polymer having an Mw around 100,000 to 500,000, which is suitable in terms of film formability and transparency.